The National Highway Traffic Safety Administration says it has two complaints that the right-front axle shaft can fail on 2013 models.

The investigation covers about 50,000 vehicles. Investigators will determine if the problem is big enough to require a recall.

No injuries or crashes have been reported.

In both complaints, owners reported a loud noise and said their SUVs wouldn't move. In both cases the vehicles had less than 5,000 miles on them.

NHTSA began its investigation on July 5, the agency said in documents posted Tuesday on its website.

In one complaint, an owner told NHTSA there was a loud bang under the SUV as it was being driven out of a subdivision. After that it would not move in drive or reverse. The owner called Hyundai's roadside assistance number, and the Santa Fe was towed to a dealership, where technicians found a cracked axle.

"They are fixing it, but I did tell them that I will be leery driving it again," the owner said in the complaint.

Owners are not identified in complaints filed with NHTSA.

Hyundai is cooperating with the investigation and says it's too early in the process to draw any conclusions, spokesman Miles Johnson said in a statement.

In a separate case, NHTSA has decided not to seek a recall of the 2011 Santa Fe because of a steering problem.

The agency began investigating about 70,000 of the SUVs in October of 2012 because a fastener could come loose, causing the steering shaft to come apart. If that happens, drivers could lose control of the SUVs. The agency received one complaint about the problem, while Hyundai had three.

NHTSA said in documents posted last week that Hyundai traced the problem to operator error at its assembly plant. The company made changes at the plant to stop the problem from happening and said it occurred on only a few vehicles. NHTSA said there haven't been any failures since the changes were made.